Barter required one or more one-on-one transfers to get to a desired result. A baker might trade bread to a dairyman for milk so that the milk to could be traded to a farmer for wheat. Money facilitated indirect transactions -- baker could his loaves to anyone for money which could be used to buy wheat -- a far more efficient process.

The key was having a medium of exchange that was believed to have a stable value and be widely accepted. The form of the money -- barley, seashells, gold coins or paper dollars -- was relevant only to the extent that fluctuations in the money supply altered its value.

To date, the value of a Bitcoin has been anything but stable. The price has varied from almost nothing at inception in 2008 to a peak above $1,200 at the end of 2013. The price then collapsed to around $550 before recovering to about $900. Meanwhile, acceptance is limited but growing.

One thing Bitcoin does not have and is never likely to get is status as legal tender for payment of taxes and debts.

So who is using the $12 billion of Bitcoins supposedly in circulation?

Criminals: Silk Road, an online purveyor of illegal drugs, accepted Bitcoins as payment. Charlie Shrem, CEO of the Bitcoin exchange BitInstant, has been arrested on charges of money laundering on behalf of Silk Road.

Speculators: Bitcoins bear more than a passing resemblance to the "funny money" NASDAQ stocks so popular with day traders and others during the Internet bubble.

Hard money investors: There are those who simply do not believe that paper money will retain its value and prefer a different store of value for their cash. While gold has been around for millennia, it cannot be easily used for day-to-day transactions in the way Bitcoins can be used.

Will Bitcoins ever go mainstream? It's highly unlikely but not impossible. For money, like beauty, is in the eye of the beholder.